High Commissioner Annan Cato urged the government on Radio Four's The World Tonight to allow her back to the UK.

He said the decision to remove her was regrettable and he appealed to the UK, which he said he considered to be a "very compassionate country".

Mr Cato said: "Even now I don't think it is too late for them to reconsider their position to allow her to come back and receive treatment. I would appeal to them to do so.

'Compassionate cases'

"I would plead that this lady come back and receive treatment in the UK. The UK has in the past done this for many, many people and I am confident they could do it again."

We will want to know who made this decision and why

Keith Vaz MP

The Commons home affairs committee says it intends questioning the head of the Border and Immigration Service, Lin Homer, about Mrs Sumani's removal.

In a statement, the Border and Immigration Agency underlined the legal grounds for the decision.

A spokesman said: "Anyone seeking to remain in the UK needs to ensure they have the legal right to do so or face removal.

"We examine with great care each individual case before removal and we assess fitness to travel and whether the necessary medical treatment is available in the country to which we are returning.

"The UK cannot offer healthcare to individuals with no legal right to remain in the UK solely because they would not be able to access a similar standard of treatment in their country of origin - this has been upheld in law.

"While it is preferable for those with no right to remain in the UK to return home voluntarily, it is regrettable that not all choose to do so and in those circumstances it may be necessary to enforce removal, this is carried out with courtesy and dignity."

But the Commons home affairs committee chairman Keith Vaz described the decision as "astonishing".

"We hope to hear a full explanation from Lin Homer about this extraordinary decision. Of course there have to be rules governing the right to remain in this country," Mr Vaz said.

"But there is also the issue of ministerial discretion in compassionate cases. The decision to remove some people and not others is becoming arbitrary and unfair...

"They just seem to be acting tough on the wrong cases. We will want to know who made this decision and why."

Kidney damage

UK officials said they had checked medical treatment was available in Ghana before she was flown home.

Less than 24 hours after being removed from the University Hospital of Wales, Cardiff, Mrs Sumani attended the main hospital in Accra, Ghana's capital city.

The mother-of-two said the hospital had then asked for the equivalent of about $6,000 (£3,060) to cover her kidney dialysis sessions for the next three months.

A hospital official in Ghana said Mrs Sumani had been accompanied by British immigration officials who had offered to pay for the first three months' treatment.

However, he said the hospital could not help her as she had no source of funding for the ongoing medical care she required.

Mrs Sumani, who has a type of cancer - malignant myeloma - which has damaged her kidneys, had been receiving dialysis three times a week in the UK before she was sent home with an expired visa.